Under preliminary terms of the agreement, the United States would sell tilt-rotor V-22 Osprey aircraft – which can take off like a helicopter but cruise at airplane speed – to Israel. It would be the first time the Pentagon has approved a foreign sale of the Osprey, which can carry combat troops and are prized for their maneuverability.

The United States also would provide Israel with KC-135 refueling planes, which could extend the range of Israeli fighters and bombers so they could be used for an attack on a country like Iran. Israel also would acquire advanced missiles for its warplanes.

Hagel has visited Israel several times previously, including during his 12 years as a Republican senator from Nebraska, but this is his first visit since he became defense secretary in February. Hagel was narrowly confirmed by the Senate after some pro-Israel groups vigorously opposed his nomination, arguing that he was insufficiently supportive of the Jewish state and too soft on Iran.

Speaking to reporters aboard his military aircraft, Hagel was reluctant to reopen that painful debate, saying that his confirmation hearing was “years ago.”

He also took pains to emphasize that the United States and Israel both regard Iran as a clear threat that must be prevented from developing nuclear weapons. He emphasized Israel’s right to self-defense and repeated that the Obama administration would not rule out military action to stop Iran from building nuclear bombs.

Israel is the first stop for Hagel on a Middle East journey that also will take him to four Arab countries: Jordan, Egypt, Saudi Arabia and the United Arab Emirates.

Saudi Arabia and the UAE are the other two countries negotiating the $10 billion arms deal. The UAE is seeking to buy 25 F-15 fighter jets and other weapons, while Saudi Arabia wants advanced missiles to equip a $30 billion fleet of F-16 aircraft that it bought from the United States in 2010.